Kondo Resonance — Impurity Spectral Function

Many-body resonance pinned at the Fermi level via spin-flip scattering

Kondo Temp T_K T_K = 15

Temperature T T = 5

Level Energy ε_d ε_d = -25

Hybridization Γ Γ = 15

Anderson impurity model: a localized d-level (at ε_d) hybridizes with a metallic band. At T < T_K, virtual spin-flip processes screen the local moment → Kondo resonance at ω=0 (Fermi level). A(ω) = (−1/π)Im G(ω), with Lorentzian Hubbard bands at ε_d ± U/2 and a narrow Kondo peak. Green curve: non-interacting; orange: full Kondo spectral function.